1. Field of the Invention
The invention relates to a display apparatus, and more particularly, to a projection apparatus.
2. Description of Related Art
With the progress in science and technology, a variety of displays applying different display principles has been constantly brought forth the new to replace the old ones, for example, to evolve from a conventional cathode ray tube (CRT) to a liquid crystal display, a plasma display, an organic light-emitting diode (OLED) display, a projection apparatus and so on.
Although a variety of displays have been constantly brought forth the new to replace the old ones, projection apparatuses are always able to maintain an indispensable role in the displays. This is because the projection apparatus is with small size/volume to produce large image frames as well as the conventional display device of which the size/volume is many times larger than the projection apparatus generates. And the projection apparatus is to spend relatively low costs to produce large image frames. In contrast, the device sizes of liquid crystal displays, plasma displays, organic light-emitting diode displays, etc., are usually slightly larger than the sizes of image frames produced by these displays, thus rapidly increasing the costs and falling short of delivering economic efficiency. Such large displays occupy relatively large space, which are not facilitated for the utilization of indoor space.
In order to produce a blending image frame with mega-size, for example, when a very large image frame is produced by blending M×N image frames together, the known techniques is utilized M×N projection apparatuses to respectively project the M×N image frames. However, utilizing M×N projection apparatuses indicates that the volume of devices becomes more than M×N times and the cost also becomes at least M×N times.
U.S. Pat. No. 7,593,629 discloses that an optical system comprises a first lens group, a second lens group, an aperture, a reflective mirror, a third lens group, a fourth lens group, and a fifth lens group using to producing images with appropriate size. In addition, Taiwan Patent Publication No. 200535547 discloses that a projection system comprises a light source, a displaying unit, a projection unit, a screen, and a driving unit.